This document discusses surface modification of nanoparticles for biomedical applications. It describes how nanoparticles can be modified on their surface with various ligands to target specific cells and tissues. These ligands include antibodies, peptides, aptamers, and other molecules like folate. Aptamers and peptides offer advantages over antibodies as targeting ligands. The document provides examples of using various ligands like VEGF, folate, and transferrin to target receptors overexpressed on cancers and other diseases. It also discusses different conjugation chemistries used to attach ligands to the nanoparticle surface, like using succinimide, biotin-streptavidin, and thiol chemistry.

1. Surface Modification of
Nanoparticles for
Biomedical Applications
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4. • Consequently a multi-component
nanomedical system can be constructed in
reverse order of controlling events, namely
from the inside out. The outer components
are the first to be used. The inner
components are the last.

6. lipids, polimers (biocompatible-biodegradable
materials)
Also water is available (liposomes)

7. The drug can be inserted into the core

8. Ligands for targeting

13. Cell Targeting
A. antibodies
B. Peptides
C. Aptamers
D. Other ligands

14. Antibodies
• Antibodies directed against tissue-specific
antigens.

15. Examples
Receptors: Vascular endothelial growth factor
(VEGF); folate (highly expressed in tumours);
Transferrin, opiod peptides (Brain),
Apolipoproteins (ApoE, Brain) , Human
epidermal growth factor (EGF)
αvβ3 Integrin
Matrix metalloproteinases

18. APTAMERS

19. Aptamers are oligonucleic acid molecules that bind a
specific target molecule. Aptamers are usually created
by selecting them from a large random sequence pool,
but natural aptamers also exist in riboswitches.
Aptamers can be used for both basic research and
clinical purposes as macromolecular drugs.

20. • aptamers offer advantages over antibodies as
they can be engineered completely in a test
tube, are readily produced by chemical
synthesis, possess desirable storage
properties, and elicit little or no
immunogenicity in therapeutic applications.

23. Aptamer target protein or molecule Application
PSMA Prostate cancer diagnosis and therapy
WT1 Understanding Wilm's tumor pathogenesis
4,4′-methylenedianiline Detecting DNA-damaging compounds
VEGF Inhibiting angiogenesis
RET Inhibition of pro-growth signaling
HER-3 Reducing drug resistance in HER-2+ cancers
TCF-1 Colon cancer growth inhibition
Tenascin-C Glioblastoma (brain cancer) detection
MUC1 Breast, pancreatic, ovarian cancers; targeting demonstrated
PDGF/PDGFR Improving transport to tumors and targeting brain cancers
NF-κB Targeting a transcription factor implicated in many diseases
Phosphatidylcholine:cholesterol liposomes Triggering liposome degradation
Raf-1 Inhibiting pro-growth signaling
αvβ3 integrin Targeting tumor-associated vasculature
Human keratinocyte growth factor Inhibiting pro-growth signali

24. Properties of aptamers versus
antibodies
Aptamers Antibodies
Binding affinity nanomolar to picomolar Binding affinity nanomolar to picomolar
Selection is a chemical process carried out Selection requires a biological system,
in vitro and can therefore target any thus it is difficult to raise antibodies
protein to toxins (not tolerated by animal) or non-
Can select for ligands under a variety of immunogenic targets.
conditions for in vitro diagnostics Limited to physiologic conditions for
diagnostics
Uniform activity regardless of batch
Screening monoclonal antibodies time
synthesis
consuming and expensive
PK parameters can be changed on demand Activity of antibodies vary from batch to
Investigator determines target site of batch
protein Difficult to modify PK parameters
Wide variety of chemical modifications to Immune system determines target site of
molecule for diverse functions of molecule protein
Return to original conformation after Temperature sensitive and undergo
temperature insult irreversible denaturation
Limited shelf-life
Unlimited shelf-life
Significant immunogenicity
No evidence of immunogenicity

25. PEPTIDES
• Peptide sequences recognized by receptors
responsible of binding can be identified and
synthesized.
• Examples are peptide sequences derived from
ApoE apolipoprotein that are recognized by
LDL receptor on cell membranes

26. Peptides aptamers
• Peptide aptamers consist of a variable peptide loop attached at
both ends to a protein scaffold. This double structural constraint
greatly increases the binding affinity of the peptide aptamer to
levels comparable to an antibody's (nanomolar range).The variable
loop length is typically comprised of 10 to 20 amino acids, and the
scaffold may be any protein which has good solubility and
compacity properties. Currently, the bacterial protein Thioredoxin-A
is the most used scaffold protein, the variable loop being inserted
within the reducing active site, which is a -Cys-Gly-Pro-Cys- loop in
the wild protein, the two Cysteines lateral chains being able to form
a disulfide bridge.Peptide aptamer selection can be made using
different systems, but the most used is currently the yeast two-
hybrid system.

27. OTHER LIGANDS
• Natural ligands for receptors can be
employed.
Examples:
Folate
ApoE
Trasferrin

35. Via succinimide
+

37. nanoparticle nanoparticle
biotin
streptavidin
biotin

38. antibody
nanoparticle
antibody
streptavidin
biotin

41. LNA
• A locked nucleic acid (LNA), often
referred to as inaccessible RNA, is a
modified RNA nucleotide. The
ribose moiety is modified with an
extra bridge connecting the 2'
oxygen and 4' carbon. LNA
nucleotides can be mixed with DNA
or RNA residues in the
oligonucleotide whenever desired.
Such oligomers are commercially
available. The locked ribose
conformation enhances base
stacking and backbone pre-
organization. This significantly
increases the hybridization
properties (melting temperature)
of oligonucleotides.[1]

46. cystein